Our simple model for the size dependence of latent heat, free of any adjustable parameter, has been extended for the size dependence of cohesive energy, or boiling heat. The cohesive energy decreases strongly when the size of particles decreases to several nanometers. The model prediction is found to be in agreement with the experimental results of W and Mo nanoparticles. (C) 2002 Elsevier Science B.V. All rights reserved.